The production of traditional fried corn snacks generally involves a prolonged steeping step of about 10 to 20 hours. Whole kernels of corn are steeped in a hot lime solution to soften the outer hull and partially gelatinize the starch in the endosperm. The degree of gelatinization is generally about 10%. As disclosed in U.S. Pat. No. 4,645,679 to Lee, III, et al., both white and yellow corn of the dent type are added to a vat containing heated water and a proportionate amount of lime. The mixture is heated to the boiling point, the heat is cut off, and the contents of the vat are allowed to stand undisturbed for 10 to 20 hours. The lime loosens the pericarp from the endosperm so that water can reach the starch and so that the pericarp can be removed. If the pericarp remains, doughs made from the steeped whole grains become excessively sticky. The corn kernels generally have a moisture content of at least about 50% by weight by the end of the steeping step. The heating and steeping steps result in hydration and partial hydrolysis of the corn hulls. The corn hulls are removed from the steeped kernels by washing. The washing may be performed with jets of water which also remove any remaining lime. The washed kernels are then ground in a stone mill into a dough containing about 50% or more moisture, known as masa.
As disclosed in U.S. Pat. No. 4,623,548 to Willard, the masa may be formed into thin pieces by extrusion, and the dough may be permitted to fall directly into hot cooking oil in a deep fat fryer. The oil replaces the water in the product resulting in a fried product having an undesirably high, for example at least 35% by weight, fat content and a hard and brittle texture. In another method, it is disclosed, a similar freshly ground masa is sheeted between rollers, cut into pieces, and baked to reduce the moisture content from about 35% to as low as about 20% before frying. According to U.S. Pat. No. 4,623,548 the dough should have a moisture content of about 50% for effective sheeting. Reducing the moisture content of the baked dough pieces reduces the fat content of the fried product to about 20% to 25%. However, according to U.S. Pat. No. 4,623,528 the fried pieces tend to have an uneven expansion, with large blistered areas and a hard, chewy texture. The same uneven structure, it is disclosed, is also found in the extruded masa-based snacks. Also, as disclosed in U.S. Pat. No. 4,645,679, the conventional process of producing corn chips has the disadvantages of producing chips which are gritty and do not easily melt in the mouth.
In the process of U.S. Pat. No. 4,645,679, hydrated corn having a moisture content of about 30% to about 40% is comminuted, and then admixed with a comminuted hydrated starch material selected from dehydrated potatoes, tapioca starch, corn starch, and mixtures thereof. However, the hydrated corn is still made by cooking raw corn kernels in water and lime, steeping until the hulls are softened, and washing the corn to remove the hulls. In a preferred embodiment the hydrated cut corn having a moisture content between about 30% and 40% is further hydrated by steeping it in water at a temperature of about 150.degree. F. to about 170.degree. F. for about 24 to about 48 hours to obtain a moisture content of about 60% to about 70%.
As disclosed in U.S. Pat. No. 4,623,548, dried masa flour has been used for the production of corn snacks and other Mexican food specialties, such as tortillas and taco shells. The dried masa flour is generally made by grinding the lime-treated corn and then dehydrating it to a stable form. A dried masa flour may then be rehydrated with water to form a dough for extrusion or sheeting. Whole corn kernels may be partially cooked, without lime treatment, that is without removing the outer hull, then dry-milled to obtain partially cooked, dry-milled whole corn flours. Doughs for making a fried snack may be produced by mixing the whole corn flour with water. However, according to U.S. Pat. No. 4,623,548 fried snacks made from whole corn flours are hard and brittle and retain too much fat because of the low water absorption of the flours. In the process of U.S. Pat. No. 4,623,548, extruded expanded fried cereal-based snack products are produced using one or more raw or partially gelatinized cereal flours such as whole corn flour, masa flour, corn flour, barley flour, bulgur flour, cracked bulgur, oat flour, rye flakes, rye flour, and soy flour. The low water-absorbing component is admixed with a high water-absorbing component such as a pregelatinized cereal starch or flour or dehydrated potatoes. In addition, a starch component comprising one or more extraneously added ungelatinized starches is included. The three components, it is disclosed, are critical at the time of frying to obtain a controlled expansion into a well expanded, uniformly porous fried snack which differs from fried corn chips. The high water absorbing component, it is disclosed, retains the water in the formed dough piece as the temperature increases during frying. Sufficient water is therefore present at the gelatinization temperature to allow the other two components to absorb water when the dough reaches the gelatinization temperature and to cause formation of an expanded, uniformly porous fried snack.
U.S. Pat. Nos. 4,873,093 and 4,834,996 to Fazzolare, et al. disclose that the machinability of doughs made from ingredients having little or no gluten may be improved by forming a dough under elevated temperature conditions, such as by steaming the ingredients.
U.S. Pat. Nos. 4,931,303 and 4,994,295 to Holm, et al. disclose that in the production of fabricated snack products having controlled surface bubbling, the dough sheet must have cohesive properties which permit the surface or surfaces of the dough or preform to stretch relatively uniformly when forming bubbles during frying. The highly cohesive, non-adhesive dough, it is disclosed, can be made by adjusting the quantity of free gelatinized starch, the degree of retrogradation of the starch (thereby affecting the water absorption of a given quantity of the starch) and the concentration of any starch-complexing emulsifiers present. In the Holm, et al. process, a dough may be formed comprising, e.g. potato solids or corn solids, raw or pre-gelatinized starches, modified starches, flavorings, oils, and the like. Dough pieces are subjected to case hardening by direct impingement gas-fired drying ovens, steam-heated conveyer dryers, infrared ovens or microwave ovens to promote surface bubbling during subsequent frying. It is disclosed that doughs containing less than about 30% moisture are generally too dry even after the Holm, et al. drying step to create adequate bubbles. In the Holm, et al. process, substantial moisture reduction of the dough is achieved by frying. During frying, the dough moisture content of about 30% to about 55% is reduced to obtain a fried product with a moisture content of about 1-2%.
German patent publication no. 4,137,161 (published May 13, 1993) to Reeg and corresponding Canadian patent publication no. 2082602 (published May 13, 1993) disclose the preparation of a maize dough for producing snack foods such as tortillas or taco shells by heating a mixture of ground corn, and water to 50-65.degree. C. which is just over the gelling point of the starch. Heating may be applied by friction from the mixing equipment or by passing steam into the mixture. The mixture is cooled while the starch is only partly gelled. The mixing of the ingredients to a homogeneous mass is preferably completed at room temperature. The mixture also contains sufficient calcium hydroxide to give a pH of 9-11.
In the present invention, corn-based products such as tortilla chips, taco shells, corn chips, soft tortillas, and soft tacos are produced using ground corn products thereby eliminating the need for prolonged steeping times associated with the production of fried corn products conventionally made from whole corn kernels. In embodiments of the invention, chip-like snacks having a crisp texture and chip-like appearance are produced from coherent, machinable, sheetable doughs without using a frying step for substantial moisture reduction of the dough thereby resulting in products having low-fat content. The corn based products of the present invention do not possess a gritty, floury, or uncooked after-taste or hard texture. The products possess a masa flavor and appearance which are comparable to those of products made using a traditional steeping process.